Dual-responsive approach with microwave-activated capsules for sustainable self-healing asphalt pavements

Microencapsulation technology offers promising approach to enhance pavement durability and longevity through self-healing mechanisms. However, conventional systems often rely on traffic-induced stresses to trigger rejuvenator release, which can limit healing efficiency and delay damage repair. This research aims to optimize alginate-based capsules by varying Water/Oil (W/O) ratios to identify compatible formulation for self-healing asphalt pavements application, ensuring uniform morphology, encapsulation efficiency, thermal and mechanical stability. Asphalt’s intrinsic self-healing properties are improved with temperature; therefore, capsules incorporating microwave absorbent materials were embedded in asphalt matrix. These materials have dual effect: heating the surrounding matrix and triggering the release of the healing agent, thereby accelerating the healing process. In this study, synthesized alginate capsules were characterized in terms of morphological, structural, thermal, and mechanical properties. The initiation of rejuvenator (Rej) release under microwave irradiation and the healing performance of asphalt mixtures were evaluated using fracture-microwave healing-fracture tests. Among the investigated formulations, capsules produced with 10:1 W/O ratio exhibited the best achieved performance, combining high thermal stability with only 2.44%weight loss at 150°C, encapsulation efficiency of 46.23%, and compressive strength of 28.31 N. The incorporation of CNT enabled rapid microwave-responsive behavior, initiating rejuvenator release within 10 s of irradiation. Asphalt mixtures containing capsules induced measurable mechanical compromise, while maintaining satisfactory performance and providing enhanced self-healing functionality. A healing index of 107.21% was achieved after only 180 s of microwave exposure, indicating recovery of peak-load resistance under the applied fracture–healing–fracture conditions. This supports the effectiveness of this dual healing technology combining microwave-induced heating and rejuvenator release.